Terminals formed from sheet metal are commonly used to connect individual electrical wires to housings that combine electrical wires into a connector. Generally, the terminals must be inserted into cavities within the housing in a particular orientation to match a mating piece in the housing. To ensure correct orientation, each terminal will typically have a protrusion or other asymmetric feature that is matched with a slot formed in the cavity.
FIG. 1 shows a prior art terminal 1 being correctly inserted (in the direction of insertion 10) into a cavity 5 formed in a housing 6. The frame of the terminal 1 is made from a single piece of sheet metal that is stamped and formed into a generally rectangular shape. This terminal 1 includes a crimping portion 11 that may be used to attach an electrical wire (not shown) to the terminal 1. Other terminals 1 may use soldering or other methods to secure the wire to the terminal 1. A protrusion 3 has been stamped from the sheet metal. The protrusion 3 has a leading side 27 and a trailing side 28. The protrusion 3 is sized and oriented to match with a slot 4 formed in a cavity 5 in the housing 6. The housing 6 may have a plurality of cavities 5 for accepting additional terminals 1. When correctly oriented as shown in FIG. 1, the terminal 1 may be inserted into the cavity 5 with little or no force to connect with a securing mechanism (not shown) housed within the cavity 5. Typically, the securing mechanism is a clip formed within the housing that snaps behind the frame of the terminal 1.
Terminals 1 such as the one shown in FIG. 1 may be used in applications requiring waterproof connectors. There are two primary methods for waterproofing connectors. One is to individually waterproof each terminal 1 in what is commonly referred to as an individually-waterproofed-cell type connector, which is shown in FIGS. 2A and 2B. The other primary approach is to use a collectively-waterproofed type connector as shown in FIG. 3.
In FIG. 2A, the terminal 1 has wire 22 crimped in the crimping portion. An individual sealing element 21 is attached to the wire 22. The sealing element 21 may be attached by crimping it onto the wire with a portion of the terminal 1, by using adhesives, or by any other method known in the art. Typically, the sealing element 21 is substantially cylindrical. In this sealing arrangement, the housing 6 may have a sealing piece 20 extending from it. The sealing piece 20 may be integrally formed with the housing (i.e. molded together), or it may be attached after manufacture. The sealing piece 20 shown in FIG. 2A is a single block formed with through holes 25 that are sized to allow the terminal 1 pass through with minimal contact. As an alternative to the single sealing piece 20, some housings 6 have hollow cylinders extending from each cavity 5. As the terminal 1 is inserted, the sealing element 21, which has a diameter larger than the width of the terminal 1, forms a seal with the sealing surface 23 inside the through hole 25. The sealing element 21 is typically rubber or some other elastomer, and the sealing piece 20 is typically plastic or resin, for example.
In FIG. 2B, a closer view of an individually-waterproofed-cell type connector is shown. The terminal 1 in FIG. 2B is similar to the terminal 1 in FIG. 2A except that in FIG. 2B, the terminal 1 has a tab 26 instead of a protrusion 3. The tab 26 performs the same function as the protrusion 3 shown in FIG. 1. The tab 26 is generally only used as an alternative to a protrusion 3 when the terminal 1 is formed with sheet metal that is sufficiently thick to not cut or otherwise damage the sealing member 24 and to have sufficient mechanical strength.
In FIG. 3, a collectively-waterproofed type connector is shown. Instead of individual sealing elements 21 as shown in FIG. 2A, a collectively-waterproofed type connector uses a single sealing member 24 to seal against wires 22 connected to multiple terminals 1. The sealing member 24 seals against an inside surface of a sealing extension 29 of the housing 6. The sealing member 24 includes multiple through holes 25 that correspond to each cavity 5 in the housing 6. The through holes 25 are sized to be smaller than the terminal 1 and the attached wire 22. The material for the sealing member 24 is typically rubber or other elastomer that is sufficiently compliant to allow the terminal 1 to pass through without tearing. After the terminal 1 passes through the sealing member 24, the sealing member 24 seals against the wire 22.
Turning to FIG. 4, a cross section of a prior art terminal 1 is shown. In FIG. 4, the terminal 1 is being incorrectly inserted into the cavity 5. The terminal 1 is oriented such that the protrusion 3 is on the opposite side of the slot 4, which is incorrect. As the terminal 1 is incorrectly inserted, the leading side 27 of the protrusion 3 contacts the housing 6. Because of the amount of interference D of the protrusion 3 with the housing 6, a normal force 12 is exerted on the protrusion 3, which is intended to prevent the incorrect insertion and alert the person or mechanism inserting the terminal 1 to the incorrect insertion.
A common problem experienced with the two-sided protrusion 3 is that it may be insufficient for preventing incorrect insertion. In some instances, a terminal 1 may be smaller than 2 mm. Accordingly, the sheet metal, from which terminal 1 is made, may be very thin. Enlarging protrusion 3 relative to the size of the terminal 1 increases interferences, which increases the resistance to incorrect insertion. However, because the protrusion is stamped from sheet metal, enlarging the protrusion 3 thins the wall of the protrusion 3, which reduces the mechanical strength of the protrusion 3. If the protrusion 3 is too weak, it will deform and allow the terminal 1 to be incorrectly inserted. This may occur regardless of the size of the terminal 1.
If the protrusion 3 is reduced in size relative to the terminal 1, it will be stronger. This, however, reduces the amount of interference D, which reduces the resistance to incorrect insertion. As a result, a person inserting the terminal 1 may accidentally force the terminal 1 into an incorrect orientation. If the smaller protrusion 3 is strong enough to not fail, it may instead damage the housing 6, which is typically made from a resin, plastic, or other material weaker than metal. This is as undesirable as a protrusion 3 that fails.
What is still needed is a protrusion that has a balance of strength and size that can be formed in the sheet metal of the terminal.